Method and mould shooter for producing mould parts, such as casting cores, for casting moulds used to cast metal melt

ABSTRACT

The invention relates to a method for the manufacture of mould parts, in particular of casting cores, for casting moulds for the casting of molten metal heats, wherein, in a shoot-moulding machine ( 1 ), with the aid of filling elements, such as shooting nozzles ( 8 ) and a shooting hood ( 6 ), material mould (F) containing an inorganic binding agent is filled into a cavity ( 12 ) of a mould tool ( 10 ) which determines the shape of the mould part (K) which is to be manufactured, wherein, heat is supplied to the mould material (F) filled into the mould tool ( 10 ), over a hardening period, in order for the mould material (F) to solidify due to the extraction of moisture, and wherein, during the hardening period, at least the filling elements ( 6,8 ) of the shoot-moulding machine ( 1 ), which contains mould material (F), and which are in a stand-by position during this hardening period, and are heated concomitantly by the radiant heat emitted by the mould tool ( 10 ), are kept at a moisture content level which prevents the solidifying of the mould material (F). In this way, mould parts for casting moulds can be manufactured reliably and with reduced defect incidence from a mould material containing an inorganic binding agent.

[0001] The invention relates to a method and shoot-moulding machine for the manufacture of mould parts, such as casting cores, for casting moulds for the casting of molten metal.

[0002] With the conventional manufacture of casting cores intended for the casting of light metal heats, as a rule a resin-bonded mould material is poured into the hollow cavity of a mould tool which determines the final shape of the casting core mould part which is to be produced. The mould tool exhibits in this situation a number of shooting openings, sufficient for the uniform filling of the cavity, through which the filling with the mould material takes place. In order to fill the mould tool, a “shooting nozzle” is introduced into each of these shooting openings, via which the mould material is then shot in. The shooting nozzles are as a rule carried together on a height-adjustable “shooting head plate”, which ensures the movement of the core box into and out of the shooting position.

[0003] In known devices, the nozzles are usually supplied via what is referred to as a “shooting hood”, which covers the shooting head plate on its side turned away from the mould tool, and is filled with mould material. To shoot in the moulding sand, the mould material contained in the shooting hood is abruptly subjected to uniform pressure by means of a gas, generally air, by means of a pressure cylinder, so that it is driven through the shooting nozzles into the mould tool.

[0004] In order to create the final strength required for the mould parts which are to be produced, there is the possibility on the one hand of incurring a chemical reaction by catalytic means in the mould material by the addition of suitable media. With this so-called “Cold Box Method”, a hardened moulded part is obtained as a result of the chemical reaction. This cannot, however, be conducted back into the cycle for the materials used for the manufacture of the moulded part.

[0005] As an alternative, the hardening can be initiated with the use of suitable binding agents by the application of heat. To carry out this method, referred to as the “Hot Box method”, known shoot-moulding machines for the manufacture of mould cores are equipped with heating units in order to heat the mould tool. The hardening of the mould material is in this case brought about by the application of heat in the mould tool.

[0006] Because the use of organic binding agents can lead to burdens on the workplace and the environment, it is a matter of concern that the organic binding agents used hitherto for the manufacture of casting cores should be replaced by such mould materials as are bonded by inorganic binding agents, such as binding agents based for example on water glass. A method which allows for the use of mould materials composed in this manner for the manufacture of core formed bodies is known from EP 0 917 499 B1.

[0007] According to this known method, a mould material is first manufactured by the mixing of an inorganic refractory mould sand with an inorganic binding agent on a water glass base. This mould material is then filled into a temperature-controlled mould tool, which is subjected to underpressure during the filling. The temperature/dwell time of the mould material after the closure of the mould tool is adjusted in this situation in such a way that a skin shell which is stable in shape and . . . of bearing is formed on the core formed body. When the core formed body has reached this state, the mould tool is opened and the core form removed. Immediately after this, the core formed body is subjected to complete drying under the effect of microwaves. In this way, moisture is drawn by physical means out of the mixture filled into the mould tool. As a result, by means of this dehydration process a hardening of the core formed body is achieved while still in the mould tool, which at least makes it possible for it to be handled in the further processing steps.

[0008] In practice, a number of deficiencies have become apparent with the carrying out of the known method in conventional devices equipped with a device for the heating of the mould tool. These are expressed, for example, in an undesirable premature hardening of the mould materials in the components of the shoot-moulding machine, which are affected by the heat irradiating from the mould tool. These components are in particular the shooting nozzles and shooting hood, which even when in a waiting position are heated to a temperature which is critical for the commencement of the hardening of the mould material because of dehydration. The premature hardening of the mould material leads, for example, to crust formation in the shooting hood on the surface of the mould material, so that the mould material can no longer be introduced in the proper manner into the mould tool, resulting in the incomplete filling of the mould tool and the clogging of the shooting nozzles. Mould material which hardens by itself in the shooting nozzles also leads to the clogging of the nozzles, with the result likewise that a uniform and proper filling is no longer guaranteed.

[0009] The object of the invention is to provide a method and device with which moulded parts for casting moulds can be manufactured, reliably and with reduced susceptibility to faults, from a mould material containing an inorganic binding agent.

[0010] Taking the prior art explained heretofore as a starting point, this object is solved by a method for the manufacture of moulded parts for casting moulds for the casting of molten metal,

[0011] Wherein, in a shoot-moulding machine, with the aid of filling elements such as shooting nozzles and shooting hood, a mould material containing an inorganic binding agent is filled into a cavity of a mould tool which determines the shape of the mould part which is to be manufactured,

[0012] Wherein heat is supplied to the mould material filled into the mould tool, over a hardening period in order for the mould material to solidify due to the extraction of moisture,

[0013] and

[0014] Wherein, during the hardening period, at least the filling elements of the shoot-moulding machine, which contains mould material, and which are in a stand-by position during this hardening period and are heated concomitantly by the radiated heat given off by the mould tool, are maintained at a moisture content level which prevents the solidifying of the mould material.

[0015] On the other hand, the object described heretofore is solved by a shoot-moulding machine for the manufacture of mould parts for casting moulds for the casting of light metal materials,

[0016] with a mould tool having a cavity, which determines the shape of the mould part which is to be manufactured,

[0017] with a heating device for heating the mould tool,

[0018] with filling elements for the introduction of mould material into the mould tool, wherein the mould tool can be moved relative to the filling elements and/or the filling elements can be moved relative to the mould tool, out of a filling position in which they are arranged closely adjacent to one another for the filling of the mould tool, into a stand-by position in which they are positioned distant from one another, and

[0019] with a moistening device which, with the filling elements located in the stand-by position, keeps those filling elements moist which contain mould sand and which lie in the radiation range of the heat emitted from the mould tool.

[0020] For preference, in this situation the mould tool is additionally capable of being moved backwards and forwards between a filling station and a removal station.

[0021] Particularly well-suited are a method according to the invention and a shoot-moulding machine according to the invention for the manufacture of casting cores for the casting of light metal melts, which in practice represent by far the largest proportion of the casting mould parts manufactured in the manner under consideration here.

[0022] According to the invention, during the hardening of the mould material filled into the heated mould tool, those parts are deliberately kept moist which are heated by the radiant heat from the mould tool up to a temperature at which the undesirable premature and therefore disruptive hardening of the mould material could set in. In this way, the extraction of water from the mould material which could otherwise occur in or at these parts as a result of the heating is counteracted, and the solidification of the mould material in the critical parts of the shoot-moulding machine will therefore be prevented. The parts which are particularly affected by the heating are in this case typically the shooting nozzles or the shooting hood required for supplying the shooting nozzles, with the shooting plate or other supply channels conducting mould materials connected to it.

[0023] Given that these parts are deliberately kept moist during the dwell time required for the hardening of the mould parts in the mould tool, this prevents, for example, both the formation of crust in the shooting hood as well as the clogging of the shooting nozzles due to the solidifying mould material. In this way, also mould materials containing inorganic water-based binding agents can be reliably used for mould parts for casting operations. The mould parts obtained are characterised by high strength and after use can be conducted back into the circle of the materials used for the manufacture of the mould.

[0024] The moistening of the parts heated by the heat emitted by the mould tool and consequently at risk with regard to the solidification of the mould material can be effected according to a first variant of the invention by at least one of the filling elements being subjected at least temporarily to a moist atmosphere during the hardening period. This embodiment of the invention is particularly well-suited for avoiding the hardening of mould material in the shooting hood, if a moist atmosphere is specifically maintained in the hood. The moisture content of the atmosphere, formed for preference by air as the carrier gas, can in this situation be adjusted with no problem to the particular circumstances. It is conceivable, for example, for the moisture content of the atmosphere surrounding the shooting nozzles in the stand-by position to be adjusted in such a way that condensation forms on the shooting nozzles and, as a result, the solidification of mould material contained in the shooting nozzles or adhering to them will be reliably avoided.

[0025] As an alternative or supplement to a moistening by the maintaining of an atmosphere of specific humidity it can be of advantage for at least one of the filling elements to be cooled at least temporarily during the hardening period. Such a specific cooling process can also induce the formation of condensation. This embodiment of the invention is therefore particularly well-suited for the protection of the shooting nozzles against clogging by solidified mould material. In addition or as an alternative to this, the shooting air itself can be moistened, in order to prevent the drying or hardening of the mould material right from the outset.

[0026] A further embodiment of the invention which is particularly easy to implement but nevertheless effective is characterised in that at least one of the filling elements which is heated concomitantly is brought at least temporarily in contact with a moisture carrier during the hardening period. This moisture carrier can be an absorbent material which is soaked with liquid, in particular water, such as a sponge or cloth. Practical tests have revealed that if such a moisture carrier is docked against shooting nozzles which are in the stand-by position, the solidification of mould material contained in the nozzles is reliably avoided.

[0027] If, in the course of the hardening time, a hot gas, for preference heated air, flows through the cavity in the mould tool at least temporarily, which is introduced dry and is drawn off loaded with moisture, the progress of the hardening of the mould part contained in the mould tool can be specifically improved. In this case, after the filling of the mould tool with mould material, during the period of time required for the hardening of the formed body and in addition to the heat introduced via the mould tool itself, a hot, dry gas flow is conducted through the mould. In this way, on the one hand the gases incurred in the course of the hardening will be conducted out of the mould tool. On the other hand additional heat will be introduced into the mould part. In this situation, this heat does not penetrate slowly via the shell of the mould part into its interior, but is actively conveyed by the gas flow into the interior of the core of the mould part.

[0028] As a result, a rapid and uniform core hardening is thus achieved. The influence of even strongly fluctuating thickness values of the core will in this way be minimised. Moulded parts obtained with the application of this variant of the proceeding according to the invention therefore already have a particularly high and homogenously distributed strength as early as when they are removed from the mould tool. At the same time, in this way cycle times can be achieved in the manufacture of casting cores which are not higher than the times which are required for the manufacture of corresponding casting cores from mould materials containing organic binding agents, in particular artificial resins.

[0029] Further advantageous embodiments of the invention are described in the dependent claims and are in the following explained in greater detail in connection with the embodiment described on the basis of the drawing. These show in diagrammatic form, in a partially sectional representation:

[0030]FIG. 1 A hoot-moulding machine for the manufacture of casting cores in a first operational position;

[0031]FIG. 2 The shoot-moulding machine represented in FIG. 1 in a second operational position.

[0032] The shoot-moulding machine 1 for the manufacture of casting cores K according to the “Hot Box method” exhibits a mixer 3. Mixed in the mixer 3 is a mould material F consisting of an inorganic refractory mould sand and a binding agent based on water glass.

[0033] This mould material F is introduced into a filling hopper 4 arranged beneath the mixer 3, from which it is conducted to a shooting cylinder 5 positioned beneath the filling hopper 4. The shooting cylinder 5 shoots the filling material F into a shooting hood 6, connected to it and widening downwards in its width and depth from the shooting cylinder 5, the shooting hood being closed on its underside by a shooting head plate 7. Formed into the shooting head plate 7 are a large number of mounts, not represented, in each of which a shooting nozzle 8 is located.

[0034] The shooting nozzles 8 extending in the direction of the cope 9 of a mould tool 10 are arranged in accordance with the shooting holes 11 formed in the cope 9. The shooting holes 11 open into a cavity 12, which is formed by corresponding recesses formed in the cope 9 and the drag box 13 of the mould tool 10. Further elements not represented here can be constituent parts of the moulding machine 1.

[0035] The shape of the casting core K which is to be manufactured is determined by the cavity 12. Venting openings 14 are formed in the drag box 13, by means of which the air displaced by the mould material F when it is filled into the cavity 12 escapes. If required, corresponding venting openings, not represented here, are located in the cope. The cope 9 and the drag box 13 of the mould tool can be heated in a controlled manner by means of a heating device 15.

[0036] Provision is made for positioning devices, not shown, in order to move the core box with the shooting holes 11 to the shooting nozzles 8 into a shooting position, in which they are located in the shooting holes 11 of the mould tool 10. In this situation, together with the shooting nozzles 8, the shooting head plate 7 secured firmly to them, the shooting hood 6, the shooting cylinder 5, and the hopper 4 are all brought together (FIG. 1).

[0037] Once the mould material F has been shot into the mould tool 10, the moulding machine 1 is moved into the stand-by position, in which the tips of the shooting nozzles 9 are arranged at a distance interval above the mould tool 10 (FIG. 2). This stand-by position is maintained by the shooting nozzles 8 until the mould material F contained in the cavity 12 of the mould tool 10 has hardened to form the casting core K as a result of the dehydration which results as a consequence of the heating of the mould material F in the mould tool. If no air flow L is conducted by over-pressure or low-pressure through the mould tool 10, in order to improve the hardening process, then the gases incurred in the course of the hardening will escape from the mould tool 10 automatically via the holes 11 and the venting openings 14.

[0038] A moistening device 16 is connected to the shooting hood 6, by means of which moist air can be conducted into the interior of the shooting hood 6. In addition to this, a sponge 17 is secured on a plate 18, which with the shooting nozzles 8 located in the stand-by position can be moved beneath the shooting nozzles 8 and raised in such a way that the sponge 17 presses against the shooting nozzles 8 and fully surrounds at least their lower section, which exhibits the nozzle opening. In addition to this, a nozzle 19 is allocated in each case to the shootting nozzle 8, by means of which, with the shooting nozzles 8 in the stand-by position, the moist air delivered from the moistening device 16 is blown onto the shooting nozzles 8.

[0039] The moisture content of the moist air introduced into the shooting hood 6 in the stand-by position and blown against the shooting nozzles 8 is determined in such a way that the mould material cannot be dehydrated. In this way the risk can be reliably prevented of the mould sand F still contained in the shooting hood 6 and the shooting nozzles 8 in the stand-by position solidifying as a result of the heating and the extraction of the water, to which the parts in question are subjected due to the radiant heat W emitted from the hot mould tool 10 both during the filling process (FIG. 1) as well as in the stand-by position (FIG. 2) which they occupy for longer.

[0040] In this situation, the sponge 17 pressed against the shooting nozzles 8 in the stand-by position also specifically ensures that no clogging of the nozzle apertures of the shooting nozzles 8 occurs as a result of clogging mould material F. The formation of condensation in the area of the shooting nozzles 8 can be further supported by the shooting nozzles 8 being cooled in the stand-by position with the aid of a cooling device, not shown here. This cooling process also reliably prevents the temperature in the interior of the shooting nozzles 8 rising to a level which is critical for the solidification of the mould material F. The moistening of the outside of the shooting nozzles 8 guarantees that no solidified mould sand F becomes baked onto the shooting nozzles 8.

[0041] In order to achieve an improved process of the hardening of the casting core K in the mould tool 10, a device 20 is provided which exhibits an air delivery connection 21 and suction extraction connection 22. During the hardening time required for the hardening of the casting core K, with the shooting nozzles 8 in the stand-by position, the air delivery connection 21 of the device 20 is coupled to the shooting holes 1 and the suction extraction connection 22 of the device 20 is coupled to venting openings 14 of the mould tool 10 (FIG. 2). In this situation, a hot, dry air flow L is constantly conducted into the mould tool 10 via the air delivery connection 21. This air flow L flows through the casting core K contained in the mould tool 10 being in the process of hardening, and is drawn off via the venting openings 14 of the mould tool 10. In this way also the interior of the core is uniformly heated, so that the moisture contained in the casting core K as a whole escapes more rapidly.

[0042] At the same time, the air flow L extracted via the suction extraction connection 22 conveys the gases incurred in the course of the heating of the casting core K in a targeted and rapid manner out of the mould tool 10. The more homogenous heat distribution attained in the casting core K by the air flow L accordingly has the effect of incurring a shortened hardening time, with improved strength of the casting core K obtained being achieved at the same time.

REFERENCE FIGURES

[0043]1 Shoot-moulding machine for the manufacture of casting cores

[0044]3 Mixer

[0045]4 Filling hopper

[0046]5 Shooting cylinder

[0047]6 Shooting head

[0048]7 Shooting head plate

[0049]8 Shooting nozzle

[0050]9 Cope

[0051]10 Mould tool

[0052]11 Shooting holes

[0053]12 Cavity

[0054]13 Drag box

[0055]14 Venting openings

[0056]15 Heating device

[0057]16 Moistening device

[0058]17 Sponge

[0059]18 Plate

[0060]19 Nozzle

[0061]20 Device for producing and suction extraction of the air flow L

[0062]21 Air delivery connection

[0063]22 Suction extraction connection

[0064] D Thickness of the casting core K

[0065] F Mould material

[0066] K Casting core

[0067] L Dry air flow

[0068] W Radiant heat 

1-20. canceled.
 21. A method for the manufacture of mould parts, in particular of casting cores, for casting moulds for the casting of molten metal, wherein in a shoot-moulding machine a with the aid of filling elements, such as shooting nozzles and shooting hood mould material containing an inorganic binding agent is filled, into a cavity of a mould tool which determines the shape of the mould part which is to be manufactured, wherein heat is supplied to the mould material filled into the mould tool over a hardening period, in order for the mould material to solidify due to the extraction of moisture, and wherein, during the hardening period, at least the filling elements of the shoot-moulding machine which contains mould material, and which are in a stand-by position during this hardening period, and are heated concomitantly by the radiant heat emitted by the mould tool, are kept at a moisture content level which prevents the solidifying of the mould material, wherein at least one of the filling elements heated concomitantly is subjected during the hardening period at least temporarily to a moist atmosphere.
 22. The method according to claim 21, wherein the atmosphere is formed by moist air.
 23. The method according to claim 21, wherein the atmosphere contains a sufficient quantity of moisture to form condensation at the filling elements heated concomitantly by the heat from the mould tool.
 24. The method according to claim 21, wherein the filling elements heated concomitantly are the shooting hood and/or the shooting cylinder, into the interior of which the moist atmosphere is introduced.
 25. The method according to claim 21, wherein during the hardening period, at least temporary, at least one of the filling elements heated concomitantly is cooled.
 26. The method according to claim 25, wherein the filling element heated concomitantly is cooled to a temperature at which moisture condenses on it or in it.
 27. The method according to claim 21, wherein during the hardening period, at least temporary, at least one of the filling elements heated concomitantly is brought into contact with a moisture carrier.
 28. The method according to claim 27, wherein the moisture carrier is an absorbent material soaked with a liquid, in particular water.
 29. The method according to claim 25, wherein the filling element heated concomitantly is at least one shooting nozzle.
 30. The method according to claim 21, wherein in the course of the hardening time the cavity of the mould tool is flowed through at least temporary by a hot gas, which is delivered dry and extracted loaded with moisture.
 31. The method according to claim 30, wherein the gas is delivered via the shooting opening of the mould tool, provided for the introduction of the at least one shooting nozzle and is led away via the venting openings of the mould tool.
 32. The method according to claim 30, wherein the gas is air.
 33. A shoot-moulding machine for the manufacture of mould parts, in particular of casting cores for casting moulds for the casting of molten metal heats with a mould tool having a cavity which determines the shape of the mould part which is to be manufactured, with a heating device for heating the mould tool, with filling elements for the introduction of mould material into the mould tool, wherein the mould tool can be moved relative to the filling elements and/or the filling elements can be moved relative to the mould tool out of a filling position in which they are arranged closely adjacent to one another for the filling of the mould tool, into a stand-by position in which they are positioned distant from one another, and with a moistening device, which, with the filling elements located in the stand-by position, keeps those filling elements moist which contain mould sand and lie in the radiation range of the heat emitted by the mould tool, wherein the moistening device is connected to a gas supply, which delivers a moist gas to the moistening device.
 34. The shoot-moulding machine according to claim 33, wherein the moistening device comprises a moisture carrierwhich, with the filling elements in the stand-by position, is in contact with at least one of these filling elements.
 35. The shoot-moulding machine according to claim 34, wherein the moisture carrier is formed by an absorbent material soaked with a liquid, in particular water.
 36. The shoot-moulding machine according to claim 33, wherein at least one of the filling elements is equipped with a cooling device, which, with the filling element in the stand-by position, cools this filling element.
 37. The shoot-moulding machine according to claim 33, wherein a dry gas supply is provided, which can be coupled to the mould tool, which, with the filling elements in the stand-by position, conducts a dry gas through the mould material present in the cavity of the mould tool.
 38. A shoot-moulding machine designed in accordance with claim 33 for the performance of the method according to claim 1 